Gandaki (Narayani / Sapta Gandaki)

The Gandaki drains the heart of the high Himalaya — Annapurna, Dhaulagiri, Manaslu and the Ganesh Himal — through the seven rivers of the Sapta Gandaki: the Kali Gandaki mainstem, the Trishuli, and the Trishuli's great feeders, the Daraundi, Seti, Madi, Marsyangdi and Budhi Gandaki. The mainstem rises as the Kali Gandaki from the Nhubine Himal glacier in Upper Mustang at 6,268 m, on the dry northern side of the main range; the rivers converge near Devghat, where the combined flow becomes the Narayani, gliding past the Chitwan lowlands to the Indian border at Tribeni (Susta) and continuing as the Gandak to the Ganga.

The basin spans roughly 46,300 km² and delivers a mean flow of about 2,025 m³/s — in the same league as the Koshi. Its signature is vertical: between Dhaulagiri (8,167 m) and Annapurna I (8,091 m) the Kali Gandaki has cut a gorge whose floor lies 5,571 m below the summits — by the summit-to-river measure, the deepest valley on Earth, carved by a river older than the mountains around it.

It is also among the most sacred of Himalayan rivers. Its upper gravels yield the black shaligram ammonite fossils revered as forms of Vishnu, the lowland river carries Vishnu's own name — Narayani — and the confluence at Devghat is one of Nepal's holiest pilgrimage and cremation sites.

Economically the Gandaki is Nepal's workhorse basin. The 144 MW Kaligandaki A at Mirmi, commissioned in 2002, was the country's largest plant for two decades, and the Marsyangdi and Trishuli corridors carry the densest clusters of hydropower in Nepal; downstream, the Narayani borders Chitwan National Park and feeds major Tarai irrigation systems.